https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111284
Bug ID: 111284
Summary: Some passing-by-value parameters are miscompiled since
GCC 9
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Keywords: accepts-invalid, rejects-valid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: de34 at live dot cn
Target Milestone: ---
GCC incorrectly rejects the following program since GCC 9
(https://godbolt.org/z/cGK1a1dqK):
```
class self_locator {
public:
self_locator() = default;
constexpr self_locator(const self_locator&) noexcept : this_{this} {}
constexpr self_locator& operator=(const self_locator&) noexcept { return
*this; }
constexpr bool valid() const noexcept { return this_ == this; }
private:
self_locator *this_ = this;
};
constexpr bool demonstrator(self_locator x) noexcept
{
return x.valid();
}
static_assert(demonstrator(self_locator{}), "");
static_assert([](self_locator x){ return x.valid(); }(self_locator{}), "");
```
The `valid` member function should always return true. But if `self_locator` is
passed by value, GCC can sometimes render the parameter in an inconsistent
state (perhaps due to incorrect bitwise copy).
